Jaw-muscle electromyography during chewing in free-ranging mantled howling monkeys at La Pacifica, Costa Rica: A pilot study

对灵长类咀嚼形态、功能和进化的研究通常分为两个研究方向之一。第一个涉及对圈养灵长类动物的实验室研究，使用肌电(EMG)等技术来量化节律性咀嚼的动力学。第二条线的研究涉及旨在捕捉灵长类摄食行为和饮食多样性的实地研究。总而言之，这些研究项目提供了压倒性和互补性的证据，证明在灵长类进化过程中，饮食和进食导致了咀嚼器官形式的适应性修改。尽管他们对灵长类咀嚼进化有共同的见解，但这些研究项目从未完全整合。此外，由于下巴肌肉功能直接受到食物的机械特性的影响，实验室研究受到必要的假设，即它们可靠地复制动物在野外的经历。为了整合这两条研究路线，PI将开发和测试一种新的系统，以记录哥斯达黎加拉帕西菲卡自由放养的尖嘴猴(Alouatta Palliata)的下颌肌肉活动。从这些猴子吃天然食物时收集的肌电数据将与这些食物的机械特性相关联，以确定颌肌功能如何随食物机械特性的变化而变化。太平洋咆哮猴是一个理想的研究样本，因为在这个自然栖息地，它们的觅食生态已经得到了很好的记录。此外，由于它们的饮食范围从树叶到水果，肌电数据可以在咀嚼具有一系列结构和机械特性的食物时被记录下来。该项目的科学价值在于它以综合的方法研究灵长类咀嚼装置中肌肉骨骼设计的进化意义。该项目将是第一个将基于实验室的记录颌肌功能的技术与灵长类摄食生态学的现场研究相结合的项目。本项目收集的数据将把咀嚼功能、饮食和自然喂养行为联系起来。通过结合这些不同的数据，我们可以开发出生态上和功能上可靠的假设，即灵长类动物对咀嚼器官的适应。此外，这些数据将解决现有的实验室提取的肌电数据是否合理地替代了各种灵长类动物可能遇到的自然环境。该项目更广泛的影响是，它将为哥斯达黎加学生提供教育机会，并为保护苍白灵芝做出贡献。学生将获得现场技术、肌电图学和机械性能数据收集和分析方面的实践培训。这种综合的方法将为他们未来在灵长类生态学、功能形态和保护方面的工作提供一个广泛的进化框架。这项研究还将有助于关于这些濒危灵长类在中南美洲不同微生境中的长期可持续性的保护管理决策。最后，该项目由一名少数族裔女性研究人员领导，从而促进了少数族裔在科学界的代表性。

Studies of primate masticatory form, function and evolution typically segregate into one of two lines of research. The first involves lab-based studies on captive primates, using techniques such as electromyography (EMG), to quantify the dynamics of rhythmic mastication. The second line of research involves field studies aimed at capturing the diversity of primate feeding behaviors and diets. Combined, these research programs provide overwhelming and complementary evidence that diet and feeding have led to adaptive modifications of masticatory apparatus form throughout primate evolution. Despite their mutual insight into primate masticatory evolution, these research programs have never been fully integrated. Moreover, because jaw-muscle function is directly influenced by the mechanical properties of foods, laboratory studies suffer from the necessary assumption that they reliably replicate what animals experience in the wild. In order to integrate these two lines of research, the PIs will develop and test a novel system to record jaw-muscle activity in free-ranging mantled howler monkeys (Alouatta palliata) at La Pacifica, Costa Rica. The EMG data collected from these monkeys while they eat their natural diets will be correlated with the mechanical properties of these foods to determine how jaw-muscle function varies with food mechanical properties. Howler monkeys at La Pacifica make an ideal study sample because their feeding ecology has been well-documented in this natural habitat. Additionally, because their diet ranges from leaves to fruits, EMG data can be recorded during the mastication of foods with a range of structural and mechanical properties.The scientific merit of this project lies in its integrative approach to studying the evolutionary significance of musculoskeletal design in the primate masticatory apparatus. This project will be the first of its kind to combine lab-based techniques for recording jaw-muscle function with field research on primate feeding ecology. Data collected in this project will link between masticatory function, diet and natural feeding behaviors. By combining these various data, we can develop ecologically and functionally robust hypotheses of primate adaptations of the masticatory apparatus. Furthermore, these data will address whether existing lab-derived EMG data are a reasonable proxy of the natural environment that various primates might encounter. The broader impacts of this project are that it will provide educational opportunities to Costa Rican students and contribute to the conservation of A. palliata. Students will get hands-on training in field techniques, electromyography, and mechanical properties data collection and analysis. This integrative approach will provide them with a broad evolutionary framework for future work on primate ecology, functional morphology and conservation. This research will also benefit conservation management decisions regarding the long-term sustainability of these endangered primates in different microhabitats in Central and South America. Finally, this project is led by a minority female researcher, thereby contributing to minority representation in the sciences.